Petroleum Charge Yield Modelling in a Chinese Lacustrine Basin

S. J. Cawley and M. E. Dunn

Petroleum charge is a critical factor within the framework of Risk, Volume and Value addressed during the evaluation of the hydrocarbon resource any basin. In the Liaodong Bay Basin, People's Republic of China, methodology was developed to describe the uncertainty in predicted charge yields from identified source rocks in terms of confidence levels (Risk), quantitation (Volume, Value) and petroleum composition (Value) in a fit-for purpose manner.

The approach taken was to:

1) define equations to calculate the mass of generated and expelled trappable petroleum per Km² of source rock within the oil and gas maturity windows, accounting for gas derived from thermal breakdown kerogen and oil-to-gas cracking in the kitchen

2) identify value ranges of parameters within the equations from available and analogue data, such as source rock thickness and potential

3) run spreadsheet-based Monte Carlo simulations of the generation-expulsion equations to calculate yield ranges of oil and gas

4) apply yield ranges with their associated confidence levels, to mapped source rock kitchens.

The result is a range of maximum trappable oil and gas yields with associated confidence levels. These must then be modified by the modelled maturity of the source rock kitchen/s - clearly an originally oil-prone source rock in the present day gas window has most likely already realised maximum oil yield but not necessarily its maximum gas yield.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California